Ingredients for Only Natural Pet dog food stew are on display during the Winter X Games in Aspen, Colorado, in this Jan. 26, 2017 file photo. The U.S. Food and Drug Administration is investigating a purported link between dog food containing legumes and potatoes as main ingredients and a potentially deadly canine heart disease called dilated cardiomyopathy. (Nathan Bilow / AP)

Dog food containing potatoes, chickpeas, lentils and other legumes as main ingredients – often marketed as “grain-free” to appeal to health-conscious pet owners who are willing to pay a premium – may be linked to a potentially deadly canine heart disease known as dilated cardiomyopathy, or DCM.

Certain large breeds are genetically predisposed to DCM, including Great Danes, Newfoundlands, Irish wolfhounds, English setters, Portuguese water dogs, St. Bernards and Doberman pinschers. With the exception of boxers and cocker spaniels, the disease is less common in small and medium breeds.

But the FDA said it became concerned after veterinarians reported dozens of cases of the disease in miniature schnauzers, golden and Labrador retrievers, a whippet, a shih tzu, a bulldog and some mixed breeds. While the number of cases remains small and researchers have not ruled out other potential causes, a common factor among those dogs was a diet heavy in legumes and potatoes – carbohydrates used to replace wheat, barley, oats and rice.

“These reports are highly unusual as they are occurring in breeds not typically genetically prone to the disease,” Dr. Martine Hartogensis, a veterinarian who serves as deputy director of the Office of Surveillance and Compliance in the FDA’s Center for Veterinary Medicine, said in a statement.

Grain-free pet foods – which also contain a variety of exotic proteins such as bison, squid, ostrich, alligator and kangaroo – have surged in popularity over the past decade, with many pet owners buying into unproven notions about gluten sensitivity and protein-rich Paleolithic diets.

“They swear up and down that it makes their dogs healthier, more energetic, better for their gut, gives them a healthier coat, all kinds of things,” said Dr. Michor Gentemann, a veterinarian at the Animal Clinic of Spokane on North Wall Street.

Gentemann and other experts, including Lisa Freeman, a veterinary nutritionist and researcher at Tufts University, say grain-free pet diets should be viewed with skepticism.

“Contrary to advertising and popular belief, there is no research to demonstrate that grain-free diets offer any health benefits over diets that contain grains,” Freeman recently told the New York Times.

“There’s none, honestly,” Gentemann said. “It’s all advertising. They have not been able to find research-based evidence that dogs are gluten-intolerant.”

That doesn’t mean his clients are wrong when they report health benefits from grain-free pet diets, Gentemann acknowledged. But he stressed that owners, especially those who home-cook their pets’ meals, should consult with veterinarians to make sure the animals are getting all the right nutrients.

Dr. Pamela Lee, an assistant professor in Washington State University’s College of Veterinary Medicine, said consumers should look for a stamp of approval by AAFCO, the Association of American Feed Control Officials, which certifies that pet food has undergone standardized clinical testing. She said the best pet foods have been used for decades without causing health problems.

It took a nationwide network of veterinary cardiologists, including Lee, to gather enough preliminary data and anecdotal evidence to bring suspicions about grain-free dog food to the FDA’s attention.

“This has been on our radar for at least a couple of years, and only recently do we feel like we have enough evidence to actually push it forward, to have it really investigated,” she said.

The pet food industry doesn’t appear to be changing course because of the FDA probe – at least not yet.

Dana Brooks, chief executive of the Pet Food Institute, which represents most pet food manufacturers, said in a statement to the New York Times: “While the exact cause of the reported illnesses has not yet been identified, PFI shares the belief that any pet illness should be taken seriously, and we remind pet owners to consult their trusted veterinarians with any questions about their pet’s health and well-being.”

Tim McGreevy, chief executive of the USA Dry Pea & Lentil Council, a national marketing organization headquartered on the state line between Pullman and Moscow, emphasized that the FDA has yet to draw any firm conclusions.

“Nutritionally complete and balanced pet food products containing pulse ingredients have been safely sold in the U.S. market for over 20 years,” McGreevy said in an email to The Spokesman-Review. “Although no causation has been shown between DCM and pulse ingredients in dog food, out of an abundance of caution, the USA Dry Pea & Lentil Council is meeting with a team of animal nutritionists, the Pet Food Institute and other experts to better understand the information that exists about these cases and other factors that could have contributed to DCM in these animals.”

Fortunately, dogs that develop the disease because of a poor diet can recover through medication, supplements and better food, Lee said.

“If you can fix the nutritional deficiency, it’s possible that these dogs’ hearts can actually go back to normal,” she said.